1. Field of the Invention
The invention relates to an electrode for a secondary battery having high capacity and excellent charging and discharging characteristics. Further, it relates to a negative electrode for a secondary battery, having, as an active substance, an alkali metal, preferably lithium metal.
2. Discussion of the Background
As an electrode for a lithium secondary battery, a conductive polymer such as polyacetylene, etc. has been proposed. However, a conductive polymer is insufficient in its doping amount of Li ions, i.e. its electrode capacity and stable charging and discharging characteristics. Also, an attempt has been made to use metallic lithium as a negative electrode of a lithium secondary battery, but in this case, the charging and discharging cycle characteristics are extremely bad.
That is, during the discharging of the battery, lithium moves as lithium ions from a negative electrode into an electrolyte. During charging, these lithium ions are again electrodeposited as metallic lithium onto the negative electrode body. When this charging and discharging cycle is repeated, the metallic lithium electrodeposited becomes dendrite-shaped. Since this dendrite-shaped metallic lithium is a very active substance, it decomposes the electrolyte, thereby causing the deterioration of the charging and discharging cycle characteristics of the battery. Further, with continued growth this dendrite-shaped metallic lithium product finally reaches a positive electrode body by penetrating through a separator, causing a short-circuit. In other words, with such a system the charging and discharging life cycle is short.
In order to avoid such problems, a negative electrode in which lithium or an alkali metal composed mainly of lithium as an active substance has been attempted which is carried on a carbonaceous material prepared by sintering an organic compound. However, by using such a negative the electrode body, the charging and discharging cycle characteristics of the negative electrode could be dramatically improved, but, on the other hand, the electrode capacity of this negative electrode was not satisfactory.